P178 Chronic Wasting Disease in European moose is associated with PrPSc features different from North American CWD
Dr Laura Pirisinu1, Dr Linh Tran2, Dr Gordon Mitchell3, Dr Aru Balachandran3, Dr Thierry Baron4, Dr Cristina Casalone5, Dr Michele Di Bari1, Dr Umberto Agrimi1. Dr Romolo Nonno1, Dr Sylvie Benestad2
1Department of Veterinary Public Health and Food Safety, Istituto Superiore di Sanita, Rome, Italy, 2Norwegian Veterinary Institute, Oslo, Norway, 3Canadian Food Inspection Agency, National and OlE Reference Laboratory for Scrapie and CWD, Ottawa Laboratory Fallowfield, Ottawa, Canada, 4Neurodeqenerative Diseases Unit, ANSES - French Agency for Food, Environmental and Occupational Health & Safety, Lyon, France, 5Istituto Zooprofilattico Sperimentale del Pietnonte, Liguria e Valle d'Aosta, Turin, Italy
Aims: In 2016, Chronic Wasting Disease (CWD) was detected for the first time in Europe in three wild Norwegian reindeer (Rangifer tarandus tarandus) and in two moose (Alces alces). The biochemical analysis and the immunohistochemical distribution of PrPSc from Norwegian reindeer revealed a pattern similar to North American (NA) isolates1. In this study, we studied the biochemical features of PrPSc from the two CWD cases in Norwegian moose.
Methods: Western blot (WB) analysis of PK-treated PrPSc (PrPres) from Norwegian moose and reindeer isolates was performed according to the ISS discriminatory WB protocol (used in BSE and scrapie Italian surveillance). PrPres fragments were determined by epitope mapping (SAF84, L42, 9A2, 12B2 mAbs), before and after deglycosylation. CWD isolates from Canadian cervids (wapiti, moose and white tailed deer) and a panel of small ruminant and bovine prion strains circulating in Europe were also analysed.
Results: WB analysis with different mAbs showed that PrPres from both Norwegian moose samples was different from that usually associated with CWD in cervids. Indeed, their main C-terminal fragment had a MW lower than the other CWD isolates, and could be discriminated by the absence of the 12B2 epitope. Furthermore, while NA CWD PrPSc is composed of a single PrPres fragment, Norwegian moose samples had an additional C-terminal PrPres fragment of ~13 kDa (CTF13). Among ovine TSEs, classical scrapie and Nor98 were discriminated from both Norwegian moose isolates, while CH1641 samples had molecular features partially overlapping with the moose, i.e. a low MW PrPres and the presence of CTF13. In contrast, moose PrPSc did not overlap with any bovine PrPSc. Indeed, the MW of moose PrPres was lower than H-BSE and similar to C-BSE and L-BSE PrPres, but the two bovine prions lacked additional PrPres fragments.
Conclusions: Unexpectedly, PrPSc from Norwegian moose revealed features substantially different from all other CWD isolates. The PrPSc pattern of Norwegian moose was also different from Canadian moose, suggesting that the variant PrPSc type observed does not simply reflect a host factor and could represent a new CWD strain. Furthermore, PrPSc of Norwegian moose can be easily discriminated from all BSE types, classical scrapie and Nor98, while showing significant overlapping only with CH1641. Bioassay in voles will help to clarify whether the different PrPSc types observed reflect the presence of a new CWD strain in Norwegian moose, and its relationships with known animal TSEs.
References: 1Benestad et al, Vet Res (2016}47:88
PRION 2017 DECIPHERING NEURODEGENERATIVE DISORDERS
please see;
***Our transmission study demonstrates that CH 1641-like scrapie is likely to be more virulent than classical scrapie in cattle.
In the US, scrapie is reported primarily in sheep homozygous for 136A/171Q (AAQQ) and the disease phenotype is similar to that seen with experimental strain CH1641.
***Our transmission study demonstrates that CH 1641-like scrapie is likely to be more virulent than classical scrapie in cattle.
P-088 Transmission of experimental CH1641-like scrapie to bovine PrP overexpression mice
Kohtaro Miyazawa1, Kentaro Masujin1, Hiroyuki Okada1, Yuichi Matsuura1, Takashi Yokoyama2
1Influenza and Prion Disease Research Center, National Institute of Animal Health, NARO, Japan; 2Department of Planning and General Administration, National Institute of Animal Health, NARO
Introduction: Scrapie is a prion disease in sheep and goats. CH1641-lke scrapie is characterized by a lower molecular mass of the unglycosylated form of abnormal prion protein (PrpSc) compared to that of classical scrapie. It is worthy of attention because of the biochemical similarities of the Prpsc from CH1641-like and BSE affected sheep. We have reported that experimental CH1641-like scrapie is transmissible to bovine PrP overexpression (TgBoPrP) mice (Yokoyama et al. 2010). We report here the further details of this transmission study and compare the biological and biochemical properties to those of classical scrapie affected TgBoPrP mice.
Methods: The details of sheep brain homogenates used in this study are described in our previous report (Yokoyama et al. 2010). TgBoPrP mice were intracerebrally inoculated with a 10% brain homogenate of each scrapie strain. The brains of mice were subjected to histopathological and biochemical analyses.
Results: Prpsc banding pattern of CH1641-like scrapie affected TgBoPrP mice was similar to that of classical scrapie affected mice. Mean survival period of CH1641-like scrapie affected TgBoPrP mice was 170 days at the 3rd passage and it was significantly shorter than that of classical scrapie affected mice (439 days). Lesion profiles and Prpsc distributions in the brains also differed between CH1641-like and classical scrapie affected mice.
Conclusion: We succeeded in stable transmission of CH1641-like scrapie to TgBoPrP mice. Our transmission study demonstrates that CH 1641-like scrapie is likely to be more virulent than classical scrapie in cattle.
WS-02
Scrapie in swine: A diagnostic challenge
Justin J Greenlee1, Robert A Kunkle1, Jodi D Smith1, Heather W. Greenlee2
1National Animal Disease Center, US Dept. of Agriculture, Agricultural Research Service, United States; 2Iowa State University College of Veterinary Medicine
A naturally occurring prion disease has not been recognized in swine, but the agent of bovine spongiform encephalopathy does transmit to swine by experimental routes. Swine are thought to have a robust species barrier when exposed to the naturally occurring prion diseases of other species, but the susceptibility of swine to the agent of sheep scrapie has not been thoroughly tested.
Since swine can be fed rations containing ruminant derived components in the United States and many other countries, we conducted this experiment to test the susceptibility of swine to U.S. scrapie isolates by intracranial and oral inoculation. Scrapie inoculum was a pooled 10% (w/v) homogenate derived from the brains of clinically ill sheep from the 4th passage of a serial passage study of the U.S scrapie agent (No. 13-7) through susceptible sheep that were homozygous ARQ at prion protein residues 136, 154, and 171, respectively. Pigs were inoculated intracranially (n=19) with a single 0.75 ml dose or orally (n=24) with 15 ml repeated on 4 consecutive days. Necropsies were done on a subset of animals at approximately six months post inoculation (PI), at the time the pigs were expected to reach market weight. Remaining pigs were maintained and monitored for clinical signs of TSE until study termination at 80 months PI or when removed due to intercurrent disease (primarily lameness). Brain samples were examined by immunohistochemistry (IHC), western blot (WB), and enzyme-linked immunosorbent assay (ELISA). Brain tissue from a subset of pigs in each inoculation group was used for bioassay in mice expressing porcine PRNP.
At six-months PI, no evidence of scrapie infection was noted by any diagnostic method. However, at 51 months of incubation or greater, 5 animals were positive by one or more methods: IHC (n=4), WB (n=3), or ELISA (n=5). Interestingly, positive bioassay results were obtained from all inoculated groups (oral and intracranial; market weight and end of study).
Swine inoculated with the agent of scrapie by the intracranial and oral routes do not accumulate abnormal prion protein (PrPSc) to a level detectable by IHC or WB by the time they reach typical market age and weight. However, strong support for the fact that swine are potential hosts for the agent of scrapie comes from positive bioassay from both intracranially and orally inoculated pigs and multiple diagnostic methods demonstrating abnormal prion protein in intracranially inoculated pigs with long incubation times.
Curriculum Vitae
Dr. Greenlee is Research Veterinary Medical Officer in the Virus and Prion Research Unit at the National Animal Disease Center, US Department of Agriculture, Agricultural Research Service. He applies his specialty in veterinary anatomic pathology to focused research on the intra- and interspecies transmission of prion diseases in livestock and the development of antemortem diagnostic assays for prion diseases. In addition, knockout and transgenic mouse models are used to complement ongoing experiments in livestock species. Dr. Greenlee has publications in a number of topic areas including prion agent decontamination, effects of PRNP genotype on susceptibility to the agent of sheep scrapie, characterization of US scrapie strains, transmission of chronic wasting disease to cervids and cattle, features of H-BSE associated with the E211 K polymorphism, and the development of retinal assessment for antemortem screening for prion diseases in sheep and cattle. Dr. Greenlee obtained his DVM degree and completed the PhD/residency program in Veterinary Pathology at Iowa State University. He is a Diplomate of the American College of Veterinary Pathologists.
Phenotype Shift from Atypical Scrapie to CH1641 following Experimental Transmission in Sheep
Marion M. Simmons*, S. Jo Moore¤a , Richard Lockey¤b , Melanie J. Chaplin, Timm Konold, Christopher Vickery, John Spiropoulos Animal and Plant Health Agency—Weybridge, Woodham Lane, Addlestone, Surrey, KT15 3NB, United Kingdom ¤a Current address: School of Veterinary and Biomedical Sciences, Murdoch University, South Street, Murdoch, Western Australia, 6150, Australia ¤b Current address: University of Southampton, Southampton, SO17 1BJ, United Kingdom * marion.simmons@apha.gsi.gov.uk
Abstract
The interactions of host and infecting strain in ovine transmissible spongiform encephalopathies are known to be complex, and have a profound effect on the resulting phenotype of disease. In contrast to classical scrapie, the pathology in naturally-occurring cases of atypical scrapie appears more consistent, regardless of genotype, and is preserved on transmission within sheep homologous for the prion protein (PRNP) gene. However, the stability of transmissible spongiform encephalopathy phenotypes on passage across and within species is not absolute, and there are reports in the literature where experimental transmissions of particular isolates have resulted in a phenotype consistent with a different strain. In this study, intracerebral inoculation of atypical scrapie between two genotypes both associated with susceptibility to atypical forms of disease resulted in one sheep displaying an altered phenotype with clinical, pathological, biochemical and murine bioassay characteristics all consistent with the classical scrapie strain CH1641, and distinct from the atypical scrapie donor, while the second sheep did not succumb to challenge. One of two sheep orally challenged with the same inoculum developed atypical scrapie indistinguishable from the donor. This study adds to the range of transmissible spongiform encephalopathy phenotype changes that have been reported following various different experimental donor-recipient combinations. While these circumstances may not arise through natural exposure to disease in the field, there is the potential for iatrogenic exposure should current disease surveillance and feed controls be relaxed. Future sheep to sheep transmission of atypical scrapie might lead to instances of disease with an alternative phenotype and onward transmission potential which may have adverse implications for both public health and animal disease control policies.
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Discussion
It is clear from all the different aspects of phenotype investigated in this study that one recipient sheep in this experimental transmission expressed a phenotype that was CH1641-like, and different from that of the donor which was diagnosed with atypical scrapie. At present this is a single event, and no conclusion can be drawn about the frequency with which this might happen either experimentally or in the field. With only two animals challenged intracerebrally, and the other recipient remaining negative, it will be impossible to extrapolate whether our finding is truly a stochastic single event, or whether a larger group size would have revealed a trend. The very small group size was an inevitable consequence of the practical limitations of this study given the decision to use only naturally-occurring field case donors, for which material is often sparse and frequently of very poor quality. However, this study provides evidence for the view that conversion/mutation of TSE strains is possible and, irrespective of whether or not such events are stochastic, they can lead to the emergence of potentially zoonotic strains.
There are a number of hypothetical explanations for this unexpected result. The first possibility that had to be excluded was that cross contamination with a CH1641 isolate might have occurred at some point in the experimental procedure. The inoculum was prepared and divided into aliquots on the day of preparation; sheep and mice were challenged using different aliquots of the same homogenate. The only strain identified in mice was atypical scrapie, which was compatible with the diagnosis in the original donor. In addition CH1641 had only been handled by the inoculum preparation team once, two years prior to the inocula for this experiment being prepared, arguing against cross contamination during the preparation of the inoculum. Therefore any possible cross contamination would have had to occur during the inoculation procedure. However, on the inoculation day no CH1641 was handled in the operating theatre—only atypical scrapie, and sterile disposable surgical equipment was used wherever possible and reusable equipment was decontaminated according to strict criteria (one hour immersion in 2M NaOH, followed by autoclaving for 18 mins at 136°C). Additionally, an audit of all prepared CH1641 samples indicated that all the anticipated samples remain in our archive and could not, therefore, have been used in error.
Another possible hypothesis is that the donor sheep might have been co-infected sub-clinically with a CH1641-like classical scrapie strain in addition to atypical scrapie. Such co-infection of different scrapie strains, while observed very rarely, has already been described in field situations [23,37], and in the laboratory context, there is supporting evidence for some heterogeneity of strain populations [38] which may then propagate differently in different hosts.
Since the donor animal was an ARR/ARR genotype, this would further reduce the likelihood of a classical scrapie strain co-existing in this sheep, since there are only two confirmed cases of classical scrapie occurring naturally in this genotype [39]. Alternatively, it could be argued that a resistant sheep could potentially be more likely to harbour low levels of a classical scrapie strain which could remain below detection levels of the currently available laboratory tests, given that little is understood about the fundamental basis for genetic resistance. However, surveillance records were reviewed for details relating to the source flock, and there has been no recorded occurrence of classical scrapie in any genotype of animal from this flock, at any time.
The third, and arguably the most plausible, explanation is that the original atypical isolate has ‘converted/mutated’ into CH1641 as a result of the experimental conditions. Again there is some precedent for this occurrence, with previous experimental observations in porcine transgenic mice, where an atypical scrapie isolate acquired a typical 3-band blot pattern with characteristics similar to sub-passaged ovine BSE [40]. This example relates to a cross-species transmission, but evidence also exists of a bovine isolate ‘converting’ or splitting in PRNP congenic TgBov mice [26]. If this was to occur in the field it could be speculated that a country such as Portugal, in which, for several years, atypical scrapie was reported in the absence of any classical scrapie, would be a good place to look for evidence of this kind of strain conversion. However, none of the few recently reported classical scrapie cases in Portugal were CH1641- like [41]. Under natural conditions, and assuming that the atypical scrapie agent is shed into the environment at all, animals are most likely exposed to only very small quantities of the agent, over a prolonged period of time, and probably by the oral route. In contrast, in the current study, a significant amount of the agent was inoculated directly to the brain thereby bypassing all potential natural physiological barriers to the disease. This may have put a greater pressure on the agent to propagate and evolve leading to the observed strain conversion. The difference of genotype between donor and recipient sheep may also have contributed to this, although this did not affect the retention of the atypical phenotype in the animal which succumbed to the oral challenge.
It is likely that it will never be possible to determine conclusively what gave rise to this change in phenotype. However, this study adds to the growing body of data which highlights a fundamental problem with prion diseases; in the absence of an agent that is structurally independent form the host genome and which can be isolated and typed, classification of natural disease relies on the phenotypic characteristics of the host. Given that some isolates appear to be unstable under certain circumstances, there is a danger in making assumptions about the disease situation in the field, and the associated public and animal health risks based on observed phenotype alone.
Supporting Information S1 File. Clinical signs of recipient animal with CH1641 scrapie. A clinical examination carried out at 514 days post inoculation reveals a bilaterally absent menace response: the sheep does not blink in response to movement of a hand/finger towards the eye but blinks when the skin surrounding the eye is touched with artery forceps. Hind limb ataxia is present (excessive swaying of the hind limbs and awkward placement of the limbs when it moves in the corner of the corridor). It bumps its head against the corner of one of the food troughs protruding into the corridor when it turns and also moves once with its head very close to the food trough after it walks from the corner towards the camera, which suggests some visual impairment. It is however able to negotiate obstacles placed on the floor of the corridor without difficulty. Camera surveillance of the pen showed abnormal lying down and rising behaviour of this sheep (identifiable by the orange arrow) compared to its pen mates (identifiable by the white circle). (MOV)
Title: Strain typing of U.S. scrapie strains using a panel of inbred mice
Author item Greenlee, Justin item Kunkle, Robert item Nicholson, Eric item Hamir, Amirali item Bulgin, Marie item Richt, Juergen Submitted to: American College of Veterinary Pathologists Meeting Publication Type: Abstract Only Publication Acceptance Date: 7/15/2008 Publication Date: 11/15/2009 Citation: Greenlee, J.J., Kunkle, R.A., Nicholson, E.M., Hamir, A.N., Bulgin, M.S., Richt, J. 2009.
Strain Typing of U.S. Scrapie Strains Using a Panel of Inbred Mice [abstract].
American College of Veterinary Pathologists. Paper No. 121. p. 762.
Interpretive Summary:
Technical Abstract:
Prion strains may vary in their ability to transmit to humans and animals. Few experimental studies have been done to provide evidence of differences between U.S. strains of scrapie, which can be distinguished by incubation times in inbred mice, microscopic lesions, immunoreactivity to various antibodies, or molecular profile (electrophoretic mobility and glycoform ratio). Recent work on two U.S. isolates of sheep scrapie supports that at least two distinct strains exist based on differences in incubation time and genotype of sheep affected. One isolate (No. 13-7) inoculated intracerebrally caused scrapie in sheep AA at codon 136 (AA136) and QQ at codon 171 (QQ171) of the prion protein in an average of 19 months post-inoculation (PI) whereas a second isolate (No. x124) caused disease in less than 12 months after oral inoculation in AV136/QQ171 sheep. Striking differences were evident when further strain analysis was done in R111, VM, C57Bl6, and C57Bl6xVM (F1) mice. No. 13-7 did not induce disease in any mouse strain at any time post-inoculation (PI) nor were brain tissues positive by western blot (WB). Positive WB results were obtained from mice inoculated with isolate No. x124 starting at day 380 PI. Incubation times averaged 508, 559, 601, and 633 days PI for RIII, C57Bl6, VM, and F1 mice, respectively. Further passage will be required to characterize these scrapie strains in mice. This work provides evidence that multiple scrapie strains exist in U.S. sheep.
Molecular Behaviors of “CH1641-Like” Sheep Scrapie Isolates in Ovine Transgenic Mice (TgOvPrP4)▿
One of these isolates (TR316211) behaved like the CH1641 isolate, with PrPres features in mice similar to those in the sheep brain. From two other isolates (O100 and O104), two distinct PrPres phenotypes were identified in mouse brains, with either high (h-type) or low (l-type) apparent molecular masses of unglycosylated PrPres, the latter being similar to that observed with CH1641, TR316211, or BSE. Both phenotypes could be found in variable proportions in the brains of the individual mice. In contrast with BSE, l-type PrPres from "CH1641-like" isolates showed lower levels of diglycosylated PrPres. From one of these cases (O104), a second passage in mice was performed for two mice with distinct PrPres profiles. This showed a partial selection of the l-type phenotype in mice infected with a mouse brain with predominant l-type PrPres, and it was accompanied by a significant increase in the proportions of the diglycosylated band. These results are discussed in relation to the diversity of scrapie and BSE strains.
In the US, scrapie is reported primarily in sheep homozygous for 136A/171Q (AAQQ) and the disease phenotype is similar to that seen with experimental strain CH1641.
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Thursday, July 14, 2011
Histopathological Studies of "CH1641-Like" Scrapie Sources Versus Classical Scrapie and BSE Transmitted to Ovine Transgenic Mice (TgOvPrP4)
SHEEP AND BSE
PERSONAL AND CONFIDENTIAL
SHEEP AND BSE
A. The experimental transmission of BSE to sheep.
Studies have shown that the ''negative'' line NPU flock of Cheviots can be experimentally infected with BSE by intracerebral (ic) or oral challenge (the latter being equivalent to 0.5 gram of a pool of four cow brains from animals confirmed to have BSE).
RB264
BSE - TRANSMISSION STUDIES
Wednesday, January 18, 2012
Selection of Distinct Strain Phenotypes in Mice Infected by Ovine Natural Scrapie Isolates Similar to CH1641 Experimental Scrapie
Journal of Neuropathology & Experimental Neurology:
February 2012 - Volume 71 - Issue 2 - p 140–147
MONDAY, MARCH 21, 2011
Sheep and Goat BSE Propagate More Efficiently than Cattle BSE in Human PrP Transgenic Mice
MONDAY, NOVEMBER 16, 2015
Docket No. APHIS-2007-0127 Scrapie in Sheep and Goats Terry Singeltary Sr. Submission
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